Porous composition utilizing n-carboxylic acid anhydrides of amino carboxylic acids



Patented Sept. 9, 1-952 H r l r 2,610,157 a ronous ooivrrosirion enumerate-1 BOXYLIC ACID amnnrnus F Ammo.

oARBoxrLIo ACIDS i e r Earl W. Gluesenkamp, Centerville, Ohio, asslgnor" to Monsanto Chemical Company, St. Louis, I

Mo.,acorporation of Delaware No Drawing. Application September This invention l relatesito new porous, resinous compositions having-unusual properties as hereinafter described. More particularly the invention relates to-flmaterials containing uniformly dispersed ftherein smallsas fllled cells. a

a claims. (01. 304.5)

24,1948, SerialNo.51,109W, j ,1?! a R -0 o, o R' l u 1 a 5 m r? M I R's J a s R o Artificial spong'edike compositions, made from natural gums and resins and from synthetic resins and rubbers, are well known to the art. They are usually made from thermoplastic polymeric compounds by compounding-the polymers with substances which evolve gases, when heated, and then heating the blended'compositionsto form numero s minute gas cells. Compositions so obtained have unusually low density and'a porous cellular structure; It is also conventional to incorporate antieoxidants. accelerators and vulcanizing agents intosynthetic or natural rubber and obtain by heating a fully cured porous composition.- 1 a One nurposeo: thi invention is'to provide new improved porous plastic compositions. A urther purpose is toprovidenew and moreefiective asentswior generating the gas within the Plastiobody. INA still further-purpose of this invention is toprovide aumeans of incorporatin reinforcing linear, polymers within the structure of'thopporousxbody simultaneously with the production ofuthe gas cellsother purposes will be evidentrinthe-following "description of the invention. x t

It has been found that whe'n'rubber or plastic compositions are compounded with N-carboxy= aminoacid anhydrides and then heated, theresultlng composition becomes porous by reason of the minute gascells forine'd by the decomposition of the anhydride. "In the blowing operation, the nonvolatile residue of thefNecarboxyamirioacid anhydridefis polymerized to form a linear polyamideywhich s rvos to reinforce the structur and to modify ltslphysical properties.

The polymerization may be a straight thermal reaction. but in thopresence of traces of initiators, for example, active hydrogen comp unds, such as water, alc hols and amines, polymerization or two units can be efiected with the simulanoous reeoncratlonof the initiator which in duces iurther polymerization in the nature of a chain (reaction: In either caseythe chen 'iical equation involved is The N-oarboxyaminoacid anhydrides maybe those derived fromthea-aminoacids, the structure of which is described in the preceding equation in which theRQ R" and R'" groups may be any alkyllor aryl. radicals. Alternatively, the aminoaci'd anhydrides may be derived from 5- amino acids in which case the anhydrides will have the following structural formula:

p t wherein the various R alkyl or and radicals.

Many of the N-carboxyaminoacid 'anhydrides are known chemical compositions, and others groups may be hydrogen,

may be prepared from the corresponding amino acids by reacting them with methyl chloroformate to form the ,N-carbomethoxyamino acid, which is then treated with thionyl chloride to formthe corresponding acid chloride, which, upon heating under lV-carboxyaminoacid anhydride. The reaction lSS8tLfOr-th in the following equations utilizing glycine as an example. a

OH -O- CAL HT-(LQH I o G=O anhydrous conditions, evolves methyl chloride and eyclizes toIorm the Suitable N-carboxyaminoaoid anhydrides are those of N-carboxyleucine, N-carboxyphenylalanine, N carboxyvaline, N-carboxytryosine and the corresponding anhydrides of other aminoacids, for example, glycine, alanine, valine, leucine, norleucine, isoleucine, isovaline, as well as aminoacids not occurring naturally which may be synthesized by conventional methods. Other useful aminoacids are those containing a radical substituted on the nitrogen atom.

The anhydrides of the N-carboxyaminoacids may be used-to generate gas cells in a wide variety of natural and synthetic plastics. Rubber derived from Hevea brasiliensis, guayule, or other natural source may be used, and also synthetic rubber, including the polymers andcopolymers of diolefins, such as isoprene, butadiene and chloroprene, particularly the copolymers of butadiene and isoprene with other polymerizable monomers, for example, styrene, acrylonitrile, acrylic and methacrylic esters, and vinyl chloride. The more useful synthetic rubbers are the copolymers of 40 to 90 percent of the diene, particularly butadiene, and from to 60 percent of the other polymerizable monomer, particularly styrene and acrylonitrile. Other useful synthetic rubbers are copolymers of one to 10 percent of the diene, for example, butadiene, isoprene and 90 to 99 percent of an isoolefin, particularly isobutylene.

In processin rubber, it is generally desirable to incorporate vulcanizing agents and the blowing agents, and thereby eifecting a cure by continuing the heating after the blowing is completed. Conventional vulcanizing agents, such as sulfur, and accelerators, for example, mag nesia, diphenyl guanidine, hexamethylenetetramine and mercaptobenzothiazole, and antioxidants, such as diaminodiphenylamine, may be added. 1

Another class of compositions which may be processed in accordance with this invention are the polymers and copolymers of vinyl chloride. This class of compositions includes polyvinyl chloride and copolymers of upward of 70 percent of vinyl chloride, and up to 30 percent of other polymerizable monomers, for example, vinyl acetate and other vinyl esters of monocarboxylic acids, methyl methacrylate and other alkyl esters of methacrylic acid, methyl acrylate and other alkyl esters of acrylic acid,"methyl maleate and'other, alkyl esters of maleic acid, methyl fumarate and other alkyl esters of fumaric acid, and vinylidine chloride.

. In processing the polymers and copolymers of vinyl chloride, it is frequently desirable to incorporatefrom five 't'o 40 percent of a suitable plasticizer to renderthe composition sufficiently fluid atblowing temperatures. Generally, these are morethermoplastic than'cured rubber, and, un less heavily plasticized, less resilient.

The new compositions areprepared by milling the plastic with from 2 to 30 percent by weight of N-carboxyaminoacid anhydride on a cold mill, or at least at a temperature below the minimum decomposition temperature of the N-carboxyaminoacid anhydride, and then confining the samplein a suitable mold in which it is heated to a temperature which induces the polymerization of the N-carboxyaminoacid anhydride, for example, 125 to 200 C. Under such conditions, the N-carboxyaminoacid anhydride polymerizes with the evolution of carbon dioxide, which forms minute gas bubbles in the polymer and produces the desirable low density and porous structure. The density of the porous compositions may be changed by varying the proportion of N-carboxyaminoacid, the most useful composition being prepared with from three to 20 percent.

Further details of the invention are set forth with respect to the following specific example.

Example A typical sponge rubber stool: having the following formulation was used.

Composition Smoked Sheets 10(5) 3 ,3 l0

2 Oleic Acid... 8.5 Gycline Oil. 23 Flectol H (Condensation product of aniline and acct 1 El-Sixty (Di (Z-bcnzothiazylthiomethyl) urea) 0.9

tion of the amino acid anhydride and the evolvedcarb'on dioxide expanded the composition to a' porous cellular structure. After twenty min-' utes of heating," the sample was cured to form tough resilient compositionsof unusually desirable porous structure. 7

The invention -'is defined by the following claims. 1

1. Porous compositions prepared by mixin a vulcanizable rubbery polymer of the group consisting'of natural rubbers and polymers of diolefinic monomers having fourto five carbon atoms, vulcanizing agents, and a compound'of the class consisting of the N-carboxylic acid anhydrides of a-amino carboxylic acids and the N- carboxylic acid anhydrides offi-amino carboxylic' acids, and heating the mixtures to decompose the N -carboxylic acid anhydride generating "poly peptides and gas cells, while simultaneously curing the rubber composition.

2. The method of preparing porous vulcanized rubber compositions which comprises mixing'a vulcanizable rubbery polymer of the group'consisting of natural rubbers and polymers of diolefinic monomers having four to five carbon atoms, vulcanizing agents, and acompound of the class consisting of the N-carboxylic' acidan hydrides of a-amino carboxylic acids and thevN-carboxylic acid anhydrides of B-amino carboxylic-acids, and heating the mixtures to the vulcanizing temperature;

3. Porous compositions prepared by mixing. a vulcanizabl rubbery polymer of the group consisting of natural rubbers and polymers of diolefinic monomers having four to five carbon atoms; vulcanizing agents and an N-carboxylicacid anhydride of an a-amino carboxylic acid, and heat.- ing the mixture to decompose the 1 I-carboxylic v acid anhydrides generatinglpolypeptides and gas cells, while simultaneously curing the rubber composition; l 4. The method of preparing porous vulcanized,

rubber compositions whichcomprises mixing a: -vulcanizable rubbery-polymer of the group oonsistin of natural rubbers and polymers of diolefinic monomers having four to five carbon atoms,

vulcanizing agents, and'an N -carboxylic acid anhydride of an a-aminotcarboxylic acid and heat ing the mixture to the vulcanizing temperature.

5. Porous compositions prepared by mixing; a vulcanizable rubbery polymer of the group consisting of natural rubbers and polymers of diolefinic monomers having four to five carbon atoms, vulcanizing agents and the N-carboxylic acid anhydride of glycine, and heating the mixture to decompose the N-carboxylic acid anhydride of glycine generatin polypeptides and gas cells, while simultaneously curing the rubber composition.

6. The method of preparing porous vulcanized rubber compositions which comprises mixing a vulcanizable rubbery polymer of the group consisting of natural rubbers and polymers of diolefinic monomers having four to five carbon atoms, vulcanizing agents, and the N-carboxylic acid anhydride of glycine and heating the mixture to the vulcanizing temperature.

EARL W. GLUESENKAMP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 5 Number OTHER REFERENCES Woodward et al., Jour. Am. Chem. Soc. pp. 1551,

' 1552', vol. 69, June 1947.

Leuchs et a1. Berichte 41, p. 1721 (1908). 

1. POROUS COMPOSITIONS PREPARED BY MIXING A VULCANIZABLE RUBBERY POLYMER OF THE GROUP CONSISTING OF NATURAL RUBBERS AND POLYMERS OF DIOLEFINIC MONOMERS HAVING FOUR TO FIVE CARBON ATOMS, VULCANIZING AGENTS, AND A COMPOUND OF THE CLASS CONSISTING OF THE N-CARBOXYLIC ACID ANHYDRIDES OF A-AMINO CARBOXYLIC ACIDS AND THE NCARBOXYLIC AND ANHYDRIDES OF B-AMINO CARBOXYLIC ACIDS, AND HEATING THE MIXTURES TO DECOMPOSE THE N-CARBOXYLIC ACID ANHYDRIDE GENERATING POLYPEPTIDES AND GAS CELLS, WHILE SIMULTANEOUSLY CURING THE RUBBER COMPOSITION. 